Image reader

ABSTRACT

An image reader is provided, which includes a first image reading unit configured to read an image on a first side of a first document sheet being conveyed on a feeding path, and output an analog signal corresponding to the read image of the first side, a second image reading unit configured to read an image on a second side opposite to the first side of the first document sheet being conveyed on the feeding path, and output a digital signal corresponding to the read image of the second side in a differential transmission method, and a processor configured to process the analog signal output from the first reading unit and the digital signal output from the second image reading unit.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 from JapanesePatent Application No. 2010-042576 filed on Feb. 26, 2010. The entiresubject matter of the application is incorporated herein by reference.

BACKGROUND

1. Technical Field

The following description relates to one or more image readersconfigured to read an image of a document sheet, particularly to one ormore image readers having a first image reading unit configured to readan image on a first side of a document sheet being conveyed along afeeding path and a second image reading unit configured to read an imageon a second side of the document sheet being conveyed along a feedingpath.

2. Related Art

So far, an image reader configured to read an image of a document sheethas been applied to various devices such as an image scanner, a copymachine, and a facsimile machine. To attain a function of the imagereader of this kind to read images on both sides of a document sheet, animage reader has been proposed that has a single image reading unitconfigured to read the images on the both sides of the document sheet byreversing the document sheet on an improved feeding path. In addition,recently, an image reader has been proposed that is configured to readimages on both sides of a document sheet together using two imagereading units. For example, in an image reader having a first imagereading unit configured to read an image on a first side of a documentsheet being conveyed along a feeding path and a second image readingunit configured to read an image on a second side of the document sheetbeing conveyed along the feeding path, it is possible to perform, inparallel, an operation of reading the image on the first side using thefirst image reading unit and an operation of reading the image on thesecond side using the second image reading unit. Thus, it is possible toenhance a reading speed for reading the both sides of the documentsheet.

SUMMARY

However, when the two image reading units are used, and a singleprocessor processes respective signals output from the two image readingunits, it might result in a so-called crosstalk due to interferencebetween the signals.

Aspects of the present invention are advantageous to provide one or moreimproved techniques for an image reader having a first image readingunit configured to read an image on a first side of a document sheetbeing conveyed along a feeding path and a second image reading unitconfigured to read an image on a second side of the document sheet beingconveyed along the feeding path, which techniques make it possible toreduce a level of crosstalk between respective signals transmitted bythe first and second image reading units to a processor.

According to aspects of the present invention, an image reader isprovided, which includes a first image reading unit configured to readan image on a first side of a first document sheet being conveyed on afeeding path, and output an analog signal corresponding to the readimage of the first side, a second image reading unit configured to readan image on a second side opposite to the first side of the firstdocument sheet being conveyed on the feeding path, and output a digitalsignal corresponding to the read image of the second side in adifferential transmission method, and a processor configured to processthe analog signal output from the first reading unit and the digitalsignal output from the second image reading unit.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 is a perspective view schematically showing a configuration of amulti-function peripheral (MFP) in an embodiment according to one ormore aspects of the present invention.

FIG. 2 is a cross-sectional view schematically showing a configurationof an image reader of the MFP in the embodiment according to one or moreaspects of the present invention.

FIG. 3 is a block diagram showing a configuration of a control system ofthe image reader in the embodiment according to one or more aspects ofthe present invention.

FIGS. 4A, 4B, and 4C exemplify signals transmitted in the image readerin the embodiment according to one or more aspects of the presentinvention.

DETAILED DESCRIPTION

It is noted that various connections are set forth between elements inthe following description. It is noted that these connections in generaland, unless specified otherwise, may be direct or indirect and that thisspecification is not intended to be limiting in this respect. Aspects ofthe invention may be implemented in computer software as programsstorable on computer-readable media including but not limited to RAMs,ROMs, flash memories, EEPROMs, CD-media, DVD-media, temporary storage,hard disk drives, floppy drives, permanent storage, and the like.

Hereinafter, an embodiment according to aspects of the present inventionwill be described with reference to the accompany drawings. As shown inFIG. 1, a multi-function peripheral (MFP) 1 includes a base body 20 anda document cover 30 provided above the base body 20 in an openable andclosable manner.

[Overall Configuration of Image Reader]

As illustrated in FIG. 2, the MFP 1 further includes a glass documenttable 21 provided on an upper end face of the base body 20. The documenttable 21 is configured such that a document sheet (not shown) is placedthereon when an image reader 10 of the embodiment is used as a flatbedscanner. The document cover 30 is attached, in an openable and closablemanner, to a side (hereinafter referred to as a rear side) of the upperend face of the base body 20 via a hinge 23 (see FIG. 1). Further, thedocument cover 30 is configured to, when closed, cover the documentsheet placed on the document table 21.

Further, as shown in FIG. 2, the document cover 30 is provided with anautomatic document feeder (ADF). Specifically, the document cover 30includes a feeding unit 100 that serves as the ADF to feed the documentsheet placed on a feed tray 110 along a feeding path, and a firstreading device 210 that is one of two reading devices 210 and 230configured to read in parallel both a first side and a second side ofthe document sheet being conveyed on a feeding path. It is noted thatthe other one of the two reading devices 210 and 230, i.e., the secondreading device 230 is provided in the base body 20.

The feeding unit 100 includes feed rollers 121 to 129 configured to feedthe document sheet placed on the feed tray 110 to a catch tray 130 alongthe feeding path (see a thick dashed line in FIG. 2). Additionally, onthe feeding path, there are provided an upstream reading position and adownstream reading position. In this case, the first reading device 210for reading an image on the first side of the document sheet is disposedin a location corresponding to the upstream reading position. It isnoted that the first side denotes a down-facing side of the documentsheet in the state placed on the feed tray 110. Further, a firstpressing member 220 is disposed on the feeding path to press thedocument sheet passing through the upstream reading position against areading surface of the first reading device 210. In addition, the secondreading device 230 for reading an image on the second side (opposite tothe first side) of the document sheet is movably provided in a location,beneath the document table 21, which corresponds to the downstreamreading position. Furthermore, a second pressing member 240 is disposedon the feeding path to press the document sheet passing through thedownstream reading position against a reading surface of the secondreading device 230.

Further, on the feeding path, an F sensor 310, an RB sensor 320, and anR sensor 330 are disposed as sensors to detect presence/absence of thedocument sheet being conveyed on respective detection positions. Thesecond reading device 230 is fixed to an endless belt 357 wound around apair of a driving pulley 353 driven by a motor 351 to rotate and adriven pulley 355. Thereby, the second reading device 230 is configuredto, in response to rotation of the motor 351, move in an auxiliaryscanning direction (i.e., a left-to-right direction in FIG. 2) under thedocument table 21.

As depicted in FIG. 1, the first reading device 210 and the secondreading device 230 are connected with a control board 450 disposedinside the base body 20, respectively via a first harness 410 and asecond harness 430 each of which is configured with a flexible flatcable (FFC). As schematically shown in FIG. 1, the second harness 430has such a sufficient length as to allow the second reading device 230to move over a whole area in the auxiliary scanning direction under thedocument table 21 (see FIG. 2). Further, the second harness 430 isprovided to join the first harness 410 near the hinge 23 and extendtoward the control board 450. The base body 20 includes therein an imageforming unit 800 configured to form an image on a sheet based on anelectrophotographic technique.

[Configuration of Control System of Image Reader]

FIG. 3 is a block diagram showing a configuration of a control system ofthe image reader 10. As shown in FIG. 3, the first reading device 210includes a contact image sensor (CIS) 211 configured to, in response toreceipt of a start signal SP, output an analog signal AO correspondingto a line of image in a main scanning direction (i.e., a directionperpendicular to plane of FIG. 2) on a pixel-by-pixel basis insynchronization with a rectangular-pulse-shaped clock signal CLK1. Thestart signal SP and the clock signal CLK1 are transferred from thecontrol board 450 via the first harness 410, and input into the CIS 211via a connector 212 disposed on an outer surface of the first readingdevice 210. Further, the analog signal AO output from the CIS 211 istransferred to the control board 450 after passing sequentially throughthe connector 212 and the first harness 410. It is noted that in FIG. 3,the single block “CIS 211” includes a plurality of elements such as alight source and lenses that form an optical path.

In the same manner as the first reading device 210, the second readingdevice 230 includes a CIS 231 configured to, in response to receipt of astart signal SP, output an analog signal AO corresponding to a line ofimage in the main scanning direction on a pixel-by-pixel basis insynchronization with a rectangular-pulse-shaped clock signal CLK2. Thestart signal SP and the clock signal CLK2 are transferred from thecontrol board 450 via the second harness 430, and input into the CIS 231after passing sequentially through a connector 232 disposed on an outersurface of the second reading device 230 and a timing generation circuit233 incorporated inside the second reading device 230.

The timing generation circuit 233 is configured to issue the startsignal SP and the clock signal CLK2 into the CIS 231 and also issue theclock signal CLK2 into a sample/hold circuit (S/H circuit) 234 and anA/D converting circuit 235. In addition, the timing generation circuit233 is configured to issue a below-mentioned sample/hold signal SH2 tothe S/H circuit 234. Specifically, the analog signal AO output from eachof the CIS 211 and the CIS 231 has a waveform of a wave delayed with apredetermined time constant as exemplified in FIGS. 4A, 4B, and 4C,which waveform results from some causes such as amplification by anamplifier incorporated inside each of the CIS 211 and the CIS 231. Thesample/hold signal SH2 is output with a form such as a trigger pulse, atsuch a moment as to acquire a value around each peak of the waveform ofthe analog signal AO, which value represents the light intensity of thelight received from each pixel in the most adequate manner.

The (analog) value, which the S/H circuit 234 acquires in response toreceipt of the sample/hold signal SH2, is converted into a digital valueby the A/D converting circuit 235 incorporated in the second readingdevice 230. Subsequently, the digital value is converted, via an LVDSinterface 238, into a digital signal DO to be transmitted in adifferential transmission method. Then, the digital signal DO istransferred to the control board 450 via the connector 232 and thesecond harness 430.

It is noted that three signal lines (“ground,” “+,” and “−”) arerequired for the differential transmission method, but a single line fortransferring the digital signal DO is shown in FIG. 3 for the sake ofsimple explanation.

The control board 450 includes a connector 451 configured to performtherethrough I/O operations (input/output operations) oftransmitting/receiving the aforementioned various signals to/from thefirst reading device 210 via the first harness, a connector 453configured to perform therethrough I/O operations oftransmitting/receiving the aforementioned various signals to/from thesecond reading device 230 via the second harness 430, and an ASIC 460configured to perform various kinds of processing. In the same fashionas the second reading device 230, the ASIC 460 includes a sample/holdcircuit (S/H) 461 and an A/D converting circuit 463 that are configuredto convert the analog signal AO transferred from the CIS 211 of thefirst reading device 210 into a digital signal.

In addition, the ASIC 460 includes a timing generation circuit 465configured to issue the sample/hold signal SH1 to the sample/holdcircuit 461 and output the aforementioned clock signals CLK1 and CLK2,start signal SP, and switch signal. The ASIC 460 further includes anLVDS interface (LVDS I/F) 467 configured to convert the digital signalDO transferred from the second reading device 230 in the differentialtransmission method into a normal digital signal. The timing generationcircuit 465 is configured to output, from a single terminal, the samestart signal SP to each of the first reading device 210 and the secondreading device 230. The start signal SP is divided into two startsignals SP outside the ASIC 460, and the two start signals SP aretransferred to the first reading device 210 and the second readingdevice 230 via the connectors 451 and 453, respectively.

The digital signals output from the A/D converting circuit 463 and theLVDS interface 467 are transferred to a bus line 469 connected with aCPU 471, a ROM 473, a RAM 475, an NVRAM 477, and an image processor 479,as well as the aforementioned timing generation circuit 465. Thereby,the ASIC 460 is allowed to perform operations such as deploying theimages read by the first reading device 210 and the second readingdevice 230 in line buffers set on the RAM 475, performing imageprocessing for the images held in the line buffers on the RAM 475 withthe image processor 479, and issuing a driving signal to the imageforming unit 800.

EFFECTS OF THE EMBODIMENT

In the image reader 10 configured as above in the embodiment, thefollowing signals are transmitted via the first harness 410 and thesecond harness 430, and it is possible to reduce a level of crosstalkbetween the signals. FIG. 4A exemplifies a signal transmitted via thefirst harness 410 in reading the images on the first and second sides ofthe document sheet. FIG. 4B exemplifies a signal transmitted via thesecond harness 430 in reading the images on the first and second sidesof the document sheet.

As illustrated in FIG. 4A, the start signal SP is transmitted to thefirst reading device 210 via the first harness 410 at a moment when thefirst reading device 210 starts reading each line of the image on thefirst side of the document sheet. In this case, the CIS 211 outputs thewave-shaped analog signal AO on a pixel-by-pixel basis insynchronization with the clock signal CLK1. The analog signal AO istransmitted to the control board 450 via the first harness 410.

Further, as illustrated in FIG. 4B, the start signal SP is transmittedto the second reading device 230 via the second harness 430 at a momentwhen the second reading device 230 starts reading each line of the imageon the second side of the document sheet. In this case, the CIS 231outputs the wave-shaped analog signal AO on a pixel-by-pixel basis insynchronization with the clock signal CLK2. Then, the S/H circuit 234acquires an analog value from the analog signal AO in response toreceipt of the sample/hold signal SH2. Thereafter, the acquired analogvalue is converted by the A/D converting circuit 235 into a digitalvalue. The digital value after the conversion is transmitted by the LVDSinterface 238 as the digital signal DO to be transmitted in thedifferential transmission method, to the control board 450 via thesecond harness 430.

As shown in FIG. 4B, the period of the clock signal CLK2 is half as longas that of the clock signal CLK1. Thus, before one line (the number ofpixels per line: N) of the analog signal AO is transmitted via the firstharness 410, the digital signal DO for each of the first pixel to theN-th pixel is completely transmitted via the second harness 430. Forthis reason, after the digital signal for the N-th pixel is output, NULdata (indicated with “Z” in FIG. 4B) is output as the digital signal DOfrom the LVDS interface 238.

Thus, in the embodiment, the signal transmitted via the first harness410 is the analog signal AO, while the signal transmitted via the secondharness 430 is the digital signal DO that is transmitted in thedifferential transmission method capable of signal transmission withlowered voltage and noise level. Therefore, in the embodiment,interference is hardly be caused between the signal transmitted via thefirst harness 410 and the signal transmitted via the second harness 430.It results in a lowered level of crosstalk between the signaltransmitted via the first harness 410 and the signal transmitted via thesecond harness 430. Accordingly, it is possible to perform accurateprocesses for the images read from the first and second sides of thedocument sheet.

Further, the second harness 430 has such a length as to allow the secondreading device 230 to move over the whole area in the auxiliary scanningdirection under the document table 21. Additionally, the second harness430 is provided to join the first harness 410 near the hinge 23 andextend toward the control board 450. When the second harness 430 hassuch a long length, the signal transmitted via the second harness 430 islikely to be noisy. Furthermore, when the second harness 430 joins thefirst harness 410, interference is likely to be caused between thesignal transmitted via the first harness 410 and the signal transmittedvia the second harness 430. In the embodiment, as described above, thedigital signal DO to be transmitted in the differential transmissionmethod is applied as a signal to be transmitted via the second harness430. Therefore, in the embodiment, it is possible to more efficientlyreduce the level of the crosstalk between the signal transmitted via thefirst harness 410 and the signal transmitted via the second harness 430.

In addition, the first reading device 210 has merely to be provided withthe CIS 211 and the connector 212, and thus can be more downsized andlightened in comparison with the second reading device 230. In theembodiment, the first reading device 210 is provided to the documentcover 30. Thereby, it is possible to provide a more preferableoperability of the document cover 30 in comparison with such aconfiguration that the second reading device 230 is provided to thedocument cover 30.

Meanwhile, the second reading device 230 is configured to performtherein signal processing up to A/D conversion. Therefore, the waveformof the analog signal AO output from the CIS 231 is less likely to bedeformed while being transferred, and thus it is possible to set thereading speed of the CIS 231 faster. For instance, as is clear from theanalog signals AO exemplified in FIGS. 4A and 4B, in the embodiment, thereading speed at which the CIS 231 reads an image of each pixel is settwice as high as that of the CIS 211.

Thus, when a reading operation is performed to read a single side of adocument sheet with the second reading device 230 disposed in thedownstream reading position, or a reading operation is performed to readonly a single side of a document sheet with the second reading device230 being moved beneath and along the document table 21, the readingoperations can be carried out at a high speed as will be mentionedbelow. Specifically, as exemplified in FIG. 4C, the aforementionedreading operations can be carried out at a speed twice as high as areading speed in double-side reading, as the start signal SP is issuedto instruct the second reading device 230 to read a next line at amoment when the NUL data (the digital signal DO indicated with thecharacter “Z”) is output from the second reading device 230 in the caseshown in FIG. 4B.

In the MFP 1 of the embodiment, for instance, it is possible to takedouble-side copy control to, after reading images on both sides of adocument sheet, cause the image forming unit 800 to form imagescorresponding to the read images on both sides of a sheet. In this case,to form the images on the both sides of the sheet takes a time twice aslong as a time taken for forming an image on a single side. Hence, eventhough the time taken for reading the both sides of the document sheetis twice as long as the time taken for reading the single side asmentioned above, it does not affect the efficiency in the double-sidecopy control.

It is noted that the CPU 471 may be configured to take facsimiletransmission control to transmit data of a read image via a modem (notshown) and/or scanning control to store the data of the read image ontoa storage device. In other words, the image reader 10 may notnecessarily be incorporated into a device having an image forming unit.

Hereinabove, the embodiment according to aspects of the presentinvention has been described. The present invention can be practiced byemploying conventional materials, methodology and equipment.Accordingly, the details of such materials, equipment and methodologyare not set forth herein in detail. In the previous descriptions,numerous specific details are set forth, such as specific materials,structures, chemicals, processes, etc., in order to provide a thoroughunderstanding of the present invention. However, it should be recognizedthat the present invention can be practiced without reapportioning tothe details specifically set forth. In other instances, well knownprocessing structures have not been described in detail, in order not tounnecessarily obscure the present invention.

Only an exemplary embodiment of the present invention and but a fewexamples of their versatility are shown and described in the presentdisclosure. It is to be understood that the present invention is capableof use in various other combinations and environments and is capable ofchanges or modifications within the scope of the inventive concept asexpressed herein. For example, the following modifications are possible.

MODIFICATIONS

The image reader 10 may have a processor, instead of the control board450 exemplified in the aforementioned embodiment, which processor isconfigured to merely perform a simple process such as attaching a timestamp to an analog signal output from the first image reading device 210and/or a digital signal output from the second reading device 230.

1. An image reader comprising: a first image reading unit configured toread an image on a first side of a first document sheet being conveyedon a feeding path, and output an analog signal corresponding to the readimage of the first side; a second image reading unit configured to readan image on a second side opposite to the first side of the firstdocument sheet being conveyed on the feeding path, and output a digitalsignal corresponding to the read image of the second side in adifferential transmission method; and a processor configured to processthe analog signal output from the first reading unit and the digitalsignal output from the second image reading unit.
 2. The image readeraccording to claim 1, further comprising: a base body; a document tablefixed to the base body, the document table being configured such that asecond document sheet is placed thereon; a first harness configured totransmit, to the processor, the analog signal output from the firstimage reading unit: and a second harness configured to transmit, to theprocessor, the digital signal output from the second image reading unit,wherein the second image reading unit is provided to the base body, andconfigured to perform any one of: a first reading operation to read theimage on the second side of the first document sheet being conveyed onthe feeding path while statically staying in the base body; and a secondreading operation to read an image on a single side of the seconddocument sheet placed on the document table while moving in apredetermined direction along the document table, and wherein the secondharness has a length that allow the second image reading unit to move inthe predetermined direction along the document table.
 3. The imagereader according to claim 2, further comprising a document cover that isattached to the base body in an openable and closable manner andconfigured to, when closed, cover the second document sheet placed onthe document table, wherein the first image reading unit comprises afirst sensor configured to read the image on the first side of the firstdocument sheet being conveyed on the feeding path, wherein the firstimage reading unit outputs the analog signal that corresponds to theimage read by the first sensor, wherein the first image reading unit isprovided to the document cover, wherein the processor comprises a firstconverter configured to convert the analog signal output from the firstimage reading unit into a first digital signal, and wherein the secondimage reading unit comprises: a second sensor configured to read one ofthe image on the second side of the first document sheet being conveyedon the feeding path and the image on the single side of the seconddocument sheet placed on the document table; a second converterconfigured to convert an analog signal corresponding to the image readby the second sensor into a second digital signal; and a differentialtransmission unit configured to output the second digital signal as thedigital signal in the differential transmission method.
 4. The imagereader according to claim 1, having an operation mode to read only theimage on the second side of the first document sheet being conveyed onthe feeding path with the second image reading unit.
 5. The image readeraccording to claim 1, wherein the second image reading unit isconfigured to read an image of each pixel at a reading speed higher thana reading speed of the first image reading unit.
 6. The image readeraccording to claim 4, wherein the second image reading unit isconfigured to read an image of each pixel at a reading speed higher thana reading speed of the first image reading unit.